/**
 * Given a collection of numbers that might contain duplicates, return all possible unique permutations.
 * For example,[1,1,2] have the following unique permutations:
 * [
 * 	[1,1,2],
 * 	[1,2,1],
 * 	[2,1,1]
 * ]
 */
/**
 * @author Ivan
 *
 */
package problem47_PermutationsII;